Recovery of solvent from hydrocarbon oils



E. R. BRowNscoMBE RECOVERY OF SOLVENT FROM HYDROCARBON OILS Aug. l5, 1939.

Filed Jan. 30, 1957 ,am m. m mm w3. Je n @Y y E X Wm.

his ZZOrne-y Patented ug. 15, 1939 Mig PATENT @FFME RECOVERY OF SGLVENT FROM HYDRO- CARBON OILS Eugene R. Brownscombc, Aldan, Pa., assigner to The Atlantic Refining Company,

Philadelphia,

Pa., a corporation of Pennsylvania Application January 30, 1937, Serial No. 123,191

11 Claims.

The present invention relates to the recovery of solvents from hydrocarbon oils, and relates more particularly to the separation and recovery of selective solvents such as the nitrated aromatic hydrocarbons, for example, nitrobenzene, chloronitrobenzene, nitrotoluene, nitronaphthalene and the like, from oils which have been selectively extracted with such solvents.

A further object of this invention is the recovery of solvents, such as the nitrated aromatic hydrocarbons, from oil, whereby vaporization or distillation of the solvent is obviated or at least reduced to a minimum.

A further object of this invention 1s the recovery of nitrated aromatic hydrocarbons, and particularly nitrobenzene, from oils which have been selectively extracted with same, by means of a second solvent which at ordinary temperature is relatively mmiscible with oil and nitrobenzene, and which, at elevated temperatures, possesses substantial solvent power for nitrobenzene but not for oil.

One of the major expenses incident to solvent extraction of hydrocarbon oils, and particularly petroleum lubricating oils, is the distillation of the solvent, most of which is present in the extract or naphthenic oil phase. In the recovery of solvents by distillation, the heat employed in vaporizing the solvent is seldom, if ever, recovered. However, in accordance with the present invention, heat losses are reduced to a minimum, since substantially all of the heating and cooling steps involve the handling of liquids without vaporization, and heat exchange may be employed with high eiciency.

Briefly, the present invention resides in an improved method of recovering selective solvents such as the nitrated aromatic hydrocarbons, for example, nitrobenzene, nitrotoluene and the like, from hydrocarbon oil which has been selectively extracted with the same. Hydrocarbon oils, and particularly lubricating oil stocks,are subjected to treatment with a nitrated aromatic hydrocarbon, such as nitrobenzene, to form a raffinate phase comprising the more paraiiinic portion of the oil together with a minor quantity of solvent, and an extract phase comprising the more naphthenic portion of the oil in solution in the major portion of the solvent. The rainate and extract phases are separated from one another, and either one or both of the phases are subjected to treatment with a second solvent for the removal of the nitrobenzene therefrom.

In the case of the recovery of the nitrated aromatic hydrocarbon, for example, nitrobenzene,

the oil-nitrobenzene mixture is brought into contact with a second solvent, which at ordinary temperature, is relatively immiscible with the nitrated aromatic hydrocarbon and with oil, but which at elevated temperatures' is substantially 5 miscible with the nitrated aromatic hydrocarbon but not with oil. lAmong the suitable secondary solvents are the hydroxy compounds, preferably the aliphatic hydroxy compounds such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol and the butyl alcohols, or mixtures of these alcohols with water. The polyhydric alcohols such as ethylene glycol, propylene glycol, and diethylene glycol and water, may likewise be employed. l5 The contacting of the oil-nitrobenzene mixture with the second solvent, e. g., the hydroxy compound, is carried on at temperatures of the order of about 250 F. to about 400 F., depending upon the character of the second solvent, and under elevated pressure suflicient to maintain said second solvent in the liquid phase. At a temperature, for example, of 350 F., the nitrobenzene is extracted from the oil to a substantial extent and a separate phase is formed comprising the hydroxy compound, the major portion of the nitrobenzene, and a small amount of oil. The remaining phase comprises essentially the bulk of the oil containing a small percentage of nitrobenzene and hydroxy compound. The phases are separated from one another, for example by decantation, and that phase comprising the hydroxy compound, the major portion of the nitrobenzene and a small quantity of oil is first cooled, preferably to a temperature of the order of about 325 F. to 250 F., or less, whereupon substantially all of the remaining oil separates from the nitrobenzene and the second solvent, e. g., the hydroxy compound.

The first cooling step is preferably carried on in such a manner that the solution is subjected to gradual cooling, whereby the oil precipitated from solution passes in countercurrent contact with the solution being cooled. Such countercurrent contacting of the precipitated oil with the solution accomplishes a maximum separation of oil from the solution, and such solution may then be subjected to the second step of cooling, whereby the nitrobenzene and second solvent are caused to separate from one another. In the second cooling step, the temperature is reduced from 250 F., for example, to 150 F. or less, whereupon the nitrobenzene and second solvent form two distinct liquid phases which may be separated from one another. Each solvent may 350 F., the

such as nitrobenzene is introduced into the uppery sectionof the extraction tower I by means of valve-controlled pipe 2 and distributing head 3, and a hydrocarbon oil, for example, a lubricating oil stock, is introduced into the lower section of tower I through valve-controlled pipe li and" distributing head 5. The nitrobenzene, being of grcaterspecic gravity than the oil, descends in counter-current contact with the oil and the more Vnaphthenic components of the oil pass into solution in the solvent, thus forming the extract phase, while the undissolved oil, containing a small portion of solvent and constitutingV the raflinate phase, is withdrawn from the top Yof the ,tower by means of valve-controlled pipe 6. The extract phase, comprising` the bulk of the solvent and containingdissolved naphthenic components, is withdrawn from the bottom of the VVtower IV through pipe 'I and is pumped byV pump B-through pipe 9 and heat exchanger I6 wherein the temperature of the extract solution is raised to about 350 F. The heated solution -from exchanger I is introduced intothe upper section of asecond contacting tower vII Yby means of valve-controlled pipe I2 and distributing head I3, andV a second solvent, for example, 50% methand-50%' water, supplied through valve-controlled pipe I4, is pumped by pump I5 through pipe I6 Vand heater I l', heated therein to about 350 F., and passed through pipe I8 and distributing head I9 into'the lower section of tower II.' Suiiicient pressure is maintained'within the system that the oil and solvents remain substantially in the liquid phase throughout the recovery operation.v heated Yextract-and the methanol-water is effected in tower II, at a temperature of the order of ing dissolved from the extract by the methanolwater.` 'I'hat portion of the oil which remains after the separation ofthe major portion of the nitrobenzene, and which contains a relatively small 'quantity of nitrobenzene and methanolwater, is withdrawn from the bottom of tower II by means of valve-controlled pipe 2D and may be passed to a stripping still (not'shown) wherein residual nitrobenzene and traces of methanolwater may be removed.

` The second solvent, i. e., methanol-water, having dissolved the major portion of the nitrobenzene and a relatively small amount of oil from the heated extract, is withdrawn'irom the top of tower II and passed ythrough valve-controlled pipe 2l Yinto cooler 22 wherein the methanol-water-nitrobenzene solution is cooled to a temperature of about 325 F.V VThe methanol-water-nitrobenzene mixture, atabcut v325 F., is passed from the cooler 22finto the lowersection of separating tower 23 by means o1" pipe 24 and distributing head 25. y' I,

Within Vthev separating tower 23, a gradually de-Y creasing temperature example, in the lower section a temperature of lphases resulting from the cooling Counter-current contacting of they major portion of the nitrobenzene be` gradient isV maintained, for

about 325 F. may obtain, and in the upper section a temperature of about 265 F., the intermediate sections gradually decreasing from 325 F.

'to 265 F. Such temperature gradient may be maintained by circulating a cooling medium through coils 25 and 21. The solution of methanol-water-nitrobenzene, containing oil which was not separated in the tower II, is passed upwardly through tower 23, wherein it is subjected Ato a gradual cooling. As a result of such cooling,

the major portion of the residual oil is thrown out of solution and'passes counter-currently downward in intimate contact with upwardly ilowing solution. Such countercurr'ent contacting results in a highly eiicient removal Yof oil from the methanol-water-nitrobenzene solution, the separated oil settling to the bottom of the tower 23, from which it is withdrawn by means of valvecontrolled pipe Y28. The oil so withdrawn may be stripped of small quantities of residual solvent,

for example, by distillation or steam-stripping (not shown). The methanol-water-nitrobenzene solution, `oontaininga small quantity of.oil, is passedfrom the upper section of separating tower 23 through pipe `29, cooled to a temperature of, for example, '70 F; in cooler 36, and introduced into separator 32 by means of valve-controlledV pipe 3|. .Thelowering of the temperature of the methanol-water-nitrobenzene mixture from about 265 F. to about 70 F. causes theV formation of two phases, one comprising methanol-water containing a small percentage of nitrobenzene and oil, and the other, nitrobenzene and a small amount of methanol-water and oil. The two step are permitted to stratify into Vlayers in separator 32, the methanol-'water being withdrawn from the upper section of the separator by means of valvecontrolled pipe 33 land reoirculated tothe recovery system by means of pump I5. The nitroben- Zene Ycontaining a small amount of methanolwater and oil is withdrawn from the lower section of separator 32 through pipe 34 and recirculated by'pump 35 through pipe 36, heat exchanger 3'!V and rvalve-controlled pipe 38 to the upper section of the extraction tower I. In the operation of the solvent extraction and recovery system, it hasbeen found that the equilibrium between the extraction solvent, for example, nitrobenzene, and the second or recovery solvent, for example, methanol-water, is practically constant. Or, in other'words, there is substantially no build-up of methanol-water in the nitrobenzene in the primary vextraction system, nor is there any buildup of nitrobenzene in methanol-water in the recovery system. In instances where the content of naphthenic oil in the recovered nitrobenzene may increasa'it is desirable to remove at least a portion of such recovered solventfrom the system for example, by means of valve-controlled pipe 39, and' subject the solvent to distillation to separate same from 'the oil. Such solvent, substantially free of oil, may be re-introduced into the primaryY extraction system through valve-controlled pipe 2.

In the above illustration of inyinvention I have shown the operation of Amy system in such a manner as to separate the initial extract, i. e., nitrobenzene and naphthenio oil, into two oil fractions dilering inr naphthenicity, and nitrobenzene substantially free of' oil; Alternatively, my system may Vbe operated to effect separation of'substantiallyfall ofY the oil, as a single oil fraction, from the nitrobenzene in the following manner. Y Y Y Referring to the drawing, the initial extract solution withdrawn from the bottom of tower I by means of pipe 'l is pumped by pump 8 through pipe 9 and heat exchanger l0 wherein the temperature of the extract solution is raised, for example, to about 350 F. The heated solution from exchanger l is passed through valve-controlled pipe lll and introduced into the separating tower 23 by means of distributing head 4l. A second or recovery solvent, for example, 50% methanol-50% water, supplied through valvecontrolled pipe Ill, is pumped by pump I through pipe IS and heater H, heated therein to a temperature of about 325 F. to 350 F. and passed through valve-controlled pipe 42 and distributing head 25 into the lower section of tower 23. Suiicient pressure is maintained within` the system that the oil and solvents remain substantially in the liquid phase throughout the recovery operation. Countercurrent contacting of the heated extract and methanol-water is effected in the lower portion of tower 23 at a temperature of about 325 F. to 350 F., the major portion of the nitrobenzene being dissolved from the extract by he methanol-water. The methanol-water-nitrobenzene solution containing a small amount of oil is passed upwardly through tower 23, the ternperature thereof being progressively reduced, for example, to about 250 F., whereby substantially all of the oil remaining in said solution is caused to precipitate therefrom and to ow countercurrently downward in contact with the upwardly flowing solution. The lower section. of the tower 23 may be maintained at a substantially constant temperature, while the middle and upper sections are progressively cooled. Or, a gradually decreasing temperature gradient may be maintained from the bottom of the tower progressively upward to the top. From the bottom of the tower 23 substantially all of the oil present in the initial extract is withdrawn, as a single oil frace tion, by means of valve-controlled pipe 28, and is passed to a distillation means (not shown) for the removal of small quantities of solvent. The methanol-Water-nitrobenzene solution, substantially free of oil is withdrawn from the top of tower 23, at a temperature of, for example, 250 F., and is then cooled to a temperature below about 150 F. to separate the nitrobenzene' from the methanol-water, as has hereinbefore beendescribed in detail. 'Ihe choice of temperatures to be employed in the various steps of my process is dependent, in general, upon the character of the aromatic nitrocompound, the oil, and the second solvent, and such temperatures are in no wise limited to those specifically shown herein.

While I have described my solvent recovery process with particular reference to the separation of solvent from the extract or naphthenic oil phase, I may also subject the raflinate or parainnic oil phase to a simiar treatment for the recovery of solvent therefrom. Furthermore, I have found that in lieu of methanol-water, I may employ other solvents, including ethyl alcohol, propyl alcohol, butyl alcohol, ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol, or mixtures of the alcohols with one another and/or with water. In the utilization of methyl and ethyl alcohol, it is generally desirable to dilute the alcohol with water to give, for example, mixtures containing 50% of alcohol and 50% of water, the water in the alcohol serving to decrease the miscibility of the mixture with hydrocarbon oil. The dilution need not be in the ratio of 1: 1, since other pro-portions may be employed, depending upon the alcohol, and the temperature and pressure conditions in the recovery system. The primary oil extraction system and/or the solvent recovery system may be of the single stage continuous countercurrent type described with reference to the drawing, or may be of the multi-stage countercurrent type, or the primary oil extraction system, may be simply of the batch type. However, it has been found that the countercurrent systems are preferable, particularly from the viewpoint of eciency and economy.

The following example is typical of the results which may be obtained in accordance with my invention:

100 bbl. per hour of an East Texas lubricating oil distillate having a Saybolt universal viscosity of 68 seconds at 210 F., an A. P. I. gravity of 21.6, and a viscosity-gravity constant of 0.862, was extracted in a 3-stage batch countercurrent extraction system at 40 F. with a mixture of recovered nitrobenzene and fresh nitrobenzene charged at a rate of 150 bbl. per hour, of which 60 bbl. per hour was fresh nitrobenzene. The recovered nitrobenzene solvent was composed of 97.5% of nitrobenzene and 2.5% of oil. There was produced a yield of 69.9 bbl. per hour of rainate phase consisting of 83.8% raffinate oil and 16.2% nitrobenzene. Upon removal of the solvent from the rainate phase, for example, by distillation and/or steam stripping, there re sulted a yield of 58.7 bbls. per hour of raffinate oil having a Saybolt universal viscosity of 58 seconds at 210 F., an A. P. I. gravity of 27.6, and a viscosity-gravity constant of 0.821. The extract phase Withdrawn.- from the primary extraction system amounted to 181 bbl. per hour and comprised a solution of 75.7% nitrobenzene and 24.3% naphthenic oil. This extract phase was charged at the rate of 181 bbl. per hour to a 3-stage batch countercurrent extraction system. and contacted at about 350 F. with a second or recovery solvent charged at a rate of 400 bbl. per hour. 'Ihe secon-d or recovery solvent was composed of 50% methyl alcohol and 50% water. There resulted from this contacting operation a yield of 25.8 bbl. per hour of a naphthenic oil solution consisting of 85.6% oil and 14.4% nitrobenzene, from which was recovered, after remo-val of the solvent by distillation, a naphthenic oil fraction amounting to 22.1. bbl. per hour and having a Saybolt universal viscosity of 100 seconds at 210 F., an A. P. I. gravity of 15.6, and a viscosity-gravity constant of 0.903.

The other phase resulting from this contacting operation amounted to 555 bbl. per hour and comprised a solution of 24.0% of nitrobenzene, 36.0% methyl alcohol, 36.0% 4.0% oil. This solution was cooled, stepwise, in a 3-stage batch countercurrent system, the 1st stage operating at 325 F., the 2nd stage at 285 F. and the 3rd stage at 265 F. The oil separated from the solution by cooling in the 3rd stage was passed to the 2nd stage, and that from the 2nd stage to the 1st stage, the final oil being withdrawn from the 1st stage, together with a portion of the solvent, i. e., nitrobenzene, which was soluble therein. In this manner there was separated, at a rate of 64.3 bbl. per hour, an oil-nitrobenzene phase consisting of 29.8% oil and 70.2% nitrobenzene, which oil, after removal of the nitrobenzene by distillation, had a Saybolt universal viscosity of 119 seconds at 210 F., an A. P. I. gravity of 11.9, and a viscosity-gravity constant of 0.933.

Water and The remaining phase produced in this 3-stage cooling system comprised a solution of 17.8% nitrobenzene, 40.8% methyl alcohol, 40.8% water and 0.6% oil, and was withdrawn from the 3rd stage (265 F.) at the rate of 490 bbl. per hour. This solution was cooled to about 70 F. and permitted to settle, whereupon there was formed a two-layer system, one phase consisting oi substantially 50% methyl alcohol and 50% Water, which phase was recirculated as the second solvent to the solvent recovery system at the rate of 400 bbl. per hour. The remaining phase, consisting of 97.5% nitrobenzene and 2.5% soil, and amounting to bbl. per hour, was added to the nitrobenzene Stripped from the rainate and eX- tract oil fractions, and the composite solvent, predominantly nitrobenzene, was recirculated to the primary oil extraction system to extract additional quantities of untreated oil.

'naphthenicity since Ysubstantially all of Y the oil may be separated from the solvent as a single oil fraction.

For example, in lieu of employing aS-stage counter-current recovery system operating at a temperature of the order of 350 F. and a 3-stage countercurrent cooling system operating at stage temperatures of 325 F., 285 F., and 265 F., respectively, I may employ a lf-stage countercurrent system in which the lst stage is maintained at, for example, 350 F., the 2nd stage at 325 F.,

the 3rd stage at 320 F., the 4th stage at 290 F.,

and a linal'separator at 70 F. .In such a system the initial extract is introduced between the 2nd and 3rd stages, While the single naphthenic oil fraction separated from the extract is Withdrawn from the lst stage at 350 and the selective solvent and second solvent Vare separated from one another and withdrawn from the nal separator at 70 F. Y Y

It will be seen that, in accordance with my invention, it is possible to recover the major portion of the primary solvent, e. g., nitrobenzene, from oil fractions substantially entirely in the liquid phase, thus eliminating, for the most part,

the necessity for distillation. Furthermore, sinceV such as ethylene glycolfpropylene glycol, buty-Y lene glycol, diethylene glycol, and mixtures thereof with one another and/or with Water and/or the monohydric alcohols.V

What I claim is: Y

1. The method of recovering a nitrated aromatic hydrocarbon from admixture with hydrocarbon oil, which comprises contacting said mixture With a solvent forrsaid nitrated aromatic hydrocarbon under elevated temperature and pressure conditions such that two liquid phases are formed, one comprising predominantly oil and the other comprising predominantly solvent and nitrated aromatic hydrocarbon, passing said phases in countercurrent contact with one another, cooling the phase comprising predominantly solvent and nitrated aromatic hydrocarbon to effect separation of residual oil from the solution of solvent and nitrated aromatic hydrocarbon, separating the oil phase from the solution and cooling said solution to separate and recover the nitrated aromatic hydrocarbon substantially free of oil. Y

2. The method of recovering a nitrated aromatic hydrocarbon from admixture with hydrocarbon oil, which comprises contacting said admixture with an alcohol under elevated temperature and-pressure conditions suchthat two liquid phases Vare formed, one comprising predominantly oil and the other comprising predominantly alcohol and nitrated aromatic hydrocarbon, passing rsaid phases in countercurrent contact with one another, cooling the phase comprising predominantly solvent and nitrated aromatic hydrocarbon to effect separation of residual oil from the solution of alcohol and nitrated aromatic hydrocarbon, separating theioil phase from the solution and cooling said solution to separate and recover the nitrated aromatic hydrocarbon substantially free of oil.

3. The method or recovering nitrobenzene from admixture with hydrocarbon oil, which comprises contacting said admixture with a solvent for said nitrobenzene under elevated temperature and pressure conditions such that two liquid phases are formed, one comprising predominantly oil and the other comprising predominantly solvent and nitrobenzene, passing said phases in countercurrent contact with one another, cooling the phase comprising predominantly solvent and nitrobenzcne to effect separation of residual oil from the solution of solvent and nitrobenzene, separating the oil phase from the solution and cooling said solution to separate and recover the nitrobenzene substantially free of oil.

4. The method of recovering nitrobenzene from admixture with hydrocarbon oil, Which comprises Y contacting said admixture with an alcohol under elevated temperature Y and pressure conditions such that two liquid phases are formed, one comprising predominantly oil and the other comprising predominantly alcohol and nitrobenzene, passing said phases-in countercurrentcontact with one another, cooling the phase comprising predominantly alcohol and nitrobenzene to eiect separation of residual oil from the solution of alcohol and nitrobenzene, separating the oil phase from the solution and cooling said solution to separate and recover the nitrobenzene substantially free of oil.

5. The method recovering a nitrated aromatic hydrocarbon from admixture With hydrocarbon oil, which comprises contacting said admixture Witha diluted alcohol under elevated temperature and pressure conditions such that tWo liquid phases are formed, one comprising predominantly oil and the other comprising predominantly dilutedv alcohol and nitrated aromatic hydrocarbon, passing said phases in countercurrent contact with one another, cooling the phase comprising predominantly diluted alcohol and nitrated aromatic hydrocarbon to eiect separation of residual oil from the solution of diluted alcohol and nitrated aromatic hydrocarbon, separating the oil phase from the solution and cooling said solution to separate and recover the nitrated aromatic hydrocarbon substantially free of oil.

6. The method of recovering nitrobenzene from admixture with hydrocarbon oil, which comprises contacting said admixture with a diluted alcohol under elevated temperature and pressure conditions such that two liquid phases are formed, one comprising predominantly oil and the other comprising predominantly diluted alcohol and nitrobenzene, passing said phases in countercurrent contact with one another, cooling the phase cornprising predominantly diluted alcohol and nitrobenzene to eect separation of residual oil from the solution of diluted alcohol and nitrobenzene, separating the oil phase from the solution and cooling said solution to separate and recover the nitrobenzene substantially free of oil.

'7. The method of recovering a nitrated aromatic hydrocarbon from admixture with hydrocarbon oil which comprises contacting said admixture with a solvent for said nitrated aromatic hydrocarbon at an elevated temperature and pressure such that two liquid phases are formed, one comprising oil containing a relatively small proportion of solvent and nitrated aromatic hydrocarbon and the other comprising solvent containing substantially the entire quantity of the nitrated aromatic hydrocarbon and a minor quantity of oil, separating the two liquid phases so formed, passing the second mentioned liquid phase through a Zone wherein the temperature is progressively reduced thereby causing substantially the entire quantity of oil to be rendered insoluble in the solvent and nitrated aromatic hydrocarbon and to pass by gravity countercurrent thereto, separately withdrawing from said Zone the oil and the solvent containing the nitrated aromatic hydrocarbon, further cooling the solvent containing the nitrated aromatic hydrocarbon, to precipitate the latter therefrom, and separating the solvent and the nitrated aromatic hydrocarbon from one another.

8. The method of recovering nitrobenzene from admixture with hydrocarbon oil which comprises contacting said admixture with an alcohol at ,an elevated temperature and pressure such that two liquid phases are formed, one comprising oil containing a relatively small proportion of alcohol and nitrobenzene and the other comprising alcohol containing substantially the entire quantity of the nitrobenzene and a minor quantity of oil, separating the two liquid phases so formed, passing the second mentioned liquid phase through a zone wherein the temperature is progressively reduced thereby causing substantially the entire quantity of oil to be rendered insoluble in the alcohol and nitrobenzene and to pass by gravity countercurrent thereto, separately withdrawing from said zone the oil and the alcohol containing the nitrobenzene, further cooling the alcohol containing the nitrobenzene to precipitate the latter from the alcohol, and separating the alcohol and the nitrobenzene from one another.

9. 'Ihe method of recovering nitrobenzene from admixture with hydrocarbon oil which comprises contacting said admixture with an alcohol at a temperature of from about 300 F. to about 400 F. and at an elevated pressure, whereby two liquid phases are formed, one comprising oil containing a relatively small proportion of alcohol and nitrobenzene and the other comprising alcohol containing substantially the entire quantity of the nitrobenzene and a minor quantity of oil, separating the two liquid phases so formed, passing the second mentioned liquid phase through a Zone wherein the temperature is progressively reduced to about 250 F., thereby causing substantially the entire quantity of oil to be rendered insoluble in the alcohol and nitrobenzene and to pass by gravity countercurrent thereto, separately withdrawing from said Zone the oil and the alcohol containing the nitrobenzene, further cooling the alcohol containing the nitrobenzene to a temperature below about 150 F. to precipitate the latter from the alcohol, and separating the alcohol and the nitrobenzene from one another.

10. The method of recovering nitrobenzene from admixture with hydrocarbon oil which comprises contacting said admixture with a diluted alcohol at a temperature of about 350 F. and at an elevated pressure, whereby two liquid phases are formed, one comprising oil containing a relatively small proportion of diluted alcohol and nitrobenzene and the other comprising diluted alcohol containing substantially the entire quantity of the nitrobenzene and a minor quantity of oil, separating the two liquid phases so formed, passing the second mentioned liquid phase through a Zone wherein the temperature is progressively reduced from about 325 F. to about 265 F., thereby causing substantially the entire quantity of oil to be rendered insoluble in the diluted alcohol and nitrobenzene and to pass by gravity countercurrent thereto, separately withdrawing from said zone the oil and the diluted alcohol containing the nitrobenzene, further cooling the diluted alcohol containing the nitrobenzene, to a temperature of about '70 F. to precipitate the latter from the diluted alcohol, and separating the diluted alcohol and the nitrobenzene from one another.

11. The method of recovering a nitrated aromatic hydrocarbon from admixture with hydrocarbon oil which comprises contacting said admixture with a solventk for said nitrated aromatic hydrocarbon at an elevated temperature and pressure such that two liquid phases are formed, one comprising oil containing a relatively small proportion of solvent and nitrated aromatic hydrocarbon and the other comprising solvent containing substantially the entire quantity of the nitrated aromatic hydrocarbon and a minor proportion of oil, separating the two liquid phases so formed, progressively cooling the second mentioned liquid phase thereby causing substantially the entire quantity of oil to be rendered insoluble in and to separate from the solvent and nitrated aromatic hydrocarbon and passing the oil so separated from the solvent and nitrated aromatic hydrocarbon countercurrent thereto during said cooling, separately withdrawing from said zione the oil and the solvent containing the nitrated aromatic hydrocarbon, further cooling the solvent containing the nitrated aromatic hydrocarbon to precipitate the latter from the solvent, and separating the solvent and the nitrated aromatic hydrocarbon from one another.

EUGENE R. BROWN SCOMBE. 

